The Spinning Dancer and the Brain

This image, originally created by Nobuyuki Kayahara, is a great scientific personality test. If you see the dancer spinning clockwise, you’ve got excess spleen qi in your left frontal crockus. This means that you’re a vibrant personality whose passions are apparent to everyone around you, but sometimes you are indecisive. If you see her spinning counter-clockwise, the right ascension of your natal chart lies in your sagittal broab and there are Fire humours dribbling out your left nostril. You should see a doctor as soon as possible.

An Australian tabloid recently republished the dancer with a little spiel about how you can use her spin as an indication of whether you are right-brained or left-brained. Since then, she’s propagated alloverthe internets, and so has the accompanying spiel.

In contrast to my deeply insightful, completely factitious interpretations of the left frontal crockus, the tabloid’s claims about “left brain” and “right brain” personality types are vastly overblown. But the spinny dancer is captivating, and because we are watching her with our brains in addition to our eyeballs, she must surely tell us something about how our brains work… so what’s actually going on?

As it happens, my fiancé is a professional optical illusion geek. He spends his time making monkeys play video games, in order to figure out their visual processing systems. So I made him explain it to me.
This much is true: you process some visual stimuli on the right side of your brain, and some on the left. You also have two optic nerves, one from the back of each eyeball. On their way to the brain these nerves meet up in a location called the optic chiasm. From the optic chiasm, information about the left side of your field of view, no matter which eye it’s coming from, is sent to the right hemisphere of your brain to be processed. Information about the right side of your field of view is sent to the left hemisphere. Therefore, if you want to see what your right brain makes of the dancer, you just need to look over to her right and watch her from your peripheral vision. Looking to her left will show you the left-brained view.

After a little practice, I can get the dancer to switch between clockwise and counter-clockwise spins – from either side of my visual field. This means both sides of my brain see both directions of spin just fine. This effect doesn’t have anything to do with differences in visual processing by the right and left sides of the brain.

Actually, the spinning dancer is an example of something called bistable perception. As an object that can be seen in either of two ways, it’s in the same class of illusion as the Necker cube and the face-vase.

Your visual system has evolved to construct a reasonable mental image of the world with a limited amount of information, and it uses a dizzying array of assumptions to do so. In the natural world these assumptions are mostly valid, and there’s only one right way to interpret any given set of signals. Artists and sundry neuroscientists, however, can consciously exploit the assumptions your brain makes about the objects it’s looking at to produce images with two or more equally valid interpretations.

When presented with stimuli that have two valid, mutually contradictory interpretations, your brain just picks one. Then, sometimes, it picks the other. We still don’t understand why this happens, or what role conscious efforts might play in this shift in perception. Many people are able to make the dancer shift directions at will, but the strategies I’ve seen almost always invoke a change of focus – I shift my attention to her feet, or scroll up and down, others look at her hands or to her side. (I’ve also seen lots of people talk about staring at her nipples, but none who report that it helps them see her change directions.)

There is absolutely nothing special about what your brain is doing when it takes some funny black shapes and turns them into a dancer who spins in both directions. Bistable stimuli are resolved using the exact same neural circuitry as everything else, and you can prove it by sticking electrodes into monkeys’ heads (e.g., Grunewald et al., 2002). You could probably prove it by sticking electrodes into your own head, too, if you felt like it. Bistable images are useful tools for experiments, because they allow us to isolate the part of visual processing where the brain is actually making a decision about how to interpret an image from the parts that are purely determined by the action at the back of your eyeball.

Bistability is not just a visual phenomenon, either – there’s an audio version called the tritone paradox. * If humans had less wimpy olfactory processing, I’m sure we could figure out some bistable smell illusions, too – though as far as I know no one has tried to confuse dogs with this particular technique.

* The way you perceive the tones in the tritone paradox is strongly related to your native language and the region in which you grew up. It’s harder to switch your perception of this paradox than it is to switch with most visual illusions, but after listening a couple times and paying attention to the overtones, I could hear the second pair of tones in the other direction.

There are lots of cool audio illusions to play with if you poke around that site. This one, which ostensibly induces your brain to pick out words related to things it has been dwelling on lately, is depressing – I default to hearing the words “no way” repeated over and over. But if I move my speakers around a little I also start to hear “burp”, “rainbow”, “wanker”, and the name of the guy in the office next door. I think I’ll stick to interpreting my dreams instead.

[...] this interests you – there is more information about optical and auditory illusions here: The Spinning Dancer and the Brain he better explains this illusion and why you see her spin in the direction that you do. [...]

[...] stuff is hooey, and you can see why it must be with a little knowledge of neural anatomy and a simple experiment.yamiTuesday, 23 October 2007 08:00:24 (Pacific Daylight Time, UTC-07:00)@Yami – thanks for the [...]

[...] want it to be, but if you are curious as to why she can be seen spinning in both directions at once check out this article, or this NY Times article, or the Wikipedia article. (And if you need it explained in plain [...]

Comments

How cool! I love optical illusions and found this one mesmerizing. I actually see the rotation both ways–if I just look away for a few moments and then look at it again, the dancer will have switched from one direction to the other. But I can’t seem to make it switch on purpose….

…and of course you can change the direction of the “spinning” by clicking on your scroll bar– sometimes once, sometimes twice, three or four times will do the trick. That way you can stop the image and see that when it changes direction it mirrors the previous image.

If you look at it indirectly, then look directly at it when its leg it pointed to one of the bottom corners, it tricks your eye to think that it is switching direction. Do it over and over and it just looks like the dancer is turning to its left and right, not in a circle…..pretty nifty.

You can prove the “Your brain just picks one” statement by clicking on the scrollbar in your browser and dragging the page up and down slightly. This forces the animation in the window to freeze or halt on certain frames, moving the scrollbar in the opposite direction gives it enough time to start up again for a frame or two. While not at all scientific, I would say my simply messing with the animation in this way results in an apparent 50/50 split between going clockwise vs. counter-clockwise.

It really is all just an illusion. We are very, very complex mechanisms, but mechanisms nonetheless.

It seems a little different than the Necker cube because it doesn’t just have ambiguous cues, it has cues that are *wrong* either way. Whichever hand/foot you pick to be in “front”, it doesn’t get bigger when it’s closer and smaller when it’s farther away – it gets a little smaller when it’s either near or far, and big when it’s on the side. And the shadow doesn’t behave like a shadow would no matter which way she’s rotating; it looks like they just took the 2-D image and flipped it 180 degrees, and moved them both up and down kind of randomly.

Although I can see her spin both directions, her shadow or mirror image, or whatever it is that is below her doesn’t make sense if she’s turning to the right. The way her shadow moves when she turns to the right isn’t possible. When she turns right, her foot and the shadow move to the left right? Right. But her shadow would keep revolving around her left foot on the opposite side of her instead of moving out of the picture. When you look at her turn left you can see that the shadow makes sense.

nice optical illusion, i had actually to cover the legs, watch torso only, not looking directly at the picture but having it in my peripherical sight. then i was able to switch the spinning direction. as soon as i uncovered the legs and shadow, it was spinning clockwise again.

I found that i can change her direction by blinking. It’s really easy for me to see her spinning left, it does get hard sometimes to blink and change the direction to the right. I don’t change my focus, move the screen or look anywhere other than where I was originally looking and I stare at the screen straight ahead!

omd……….. i just made it move clockwise then anticlockwise on purpose hehe u have to be able to pretend that the shadow is going clockwise or anticlockwise to be able to change the way in which she is going!

Annie…it means the hemispheres of your brain are switched, with the left hemisphere where the right should be, and the right where the left should be. Or your hemispheres are correctly placed, but your eyeballs are switched. You should consider seeing a doctor and having them switched back.

The illusiong is too simple.Clockwise or counter-clockwise depends on where are you. Look from the head,it is clockwise;and look from the feet,it is conter-clockwise. It cannot tell the difference of the brain.

Whether you see the dancer moving clockwise or anti-clockwise depends on whether you choose to examine her axis from above or beneath.

If you look at the turning axis from above that means she is turning clockwise. However, if you view the turning axis from beneath that means she is turning counter-clockwise.

Test this: Point your index finger up and, at chest level, rotate your hand clockwise on the transverse plane (ie the floor or table represent transverse planes, your mirror does not).
Now, still rotating the hand the same way, raise it above your head. It will now appear to be moving counter-clockwise.

How the image works: First, the model leans back and rotates on a diagonal axis so that your view of her rotates between slanted downward and slanted upward. Second, the model is moving up and down. Depending on which up-down slant or up-down movement you unconsciously fix on either the above or below perspective of the turning axis.

@Jizzle: Of course it will change directions twice. Your brain cannot process two optical illusions, much more THE SAME optical illusions, twice. You can only process one.

If your brain can see two or more similar optical illusions like that one, moving in counter and clockwise, then you are not from this Planet.

If you think it is “timed” then do this:
1) Duplicate the image yourself; or
2) Write down in a piece of paper the number of minutes each direction changes occured to you;
3) Repeat #2 up to 5 times.
4) Compare your results.

You will see that you have different time span for each directional switch of the girl.

Its a front and back issue, for in drawing, one requires overlap to help force things into distance, but in this image, there is no clue as to what is front or back, so your brain has to make an assumption, and both assumptions are similarly compelling. The switch happens because you switch which arm/leg is overlapping the other. Since there is no visual indication, it can go either way, at first like magic, then once you understand, whatever your preference.

took me about 30 seconds to get the change in direction going.
had a closer look at it and worked out how it works.
its a matter of perspective.
the image is not 3D and because it is black you cannot tell wether you are
looking at the front or the or the back of the girl,except when she is side on and
when she is side on you cannot tell wether you are looking at her left side or her right side.
so depending on which perspective your brain takes she will spin one way or the other.
change your perspective and you change the direction.
with a bit of practice you can change her direction every half rotation.

I checked this out a while ago, surprisingly I can get my mind to view it both ways. I first saw it moving clock-wise, I focused a bit and saw it moving couter-clock wise. Still a pretty interesting thing though. :)

@ Kent, the image is not actually spinning its moving from side to side. that means that the spinning is all in your head. there is no right or wrong answer, and there is no view from above. oh and by the way, i can change which way its spinning on command now.

I have seen the dancer spin in both directions; it’s a matter of concentration. In fact, it helps to stimulate the brain with a few push-ups. After 20 push-ups, I regarded the image, and she spun clockwise. But after two mintues, she magically slipped into counter-clockwise. Visually, focus on her face in order to catch both directions.

this is actually fake … the image changes direction by itself … have a group of friends watch it with you … you’ll all notice the direction change at the same time (not your brain interpreting but the direction changing by itself)

There is no big deal about this. The person who created this, did so that the lady spins both ways. Nobody’s mind makes it goes into any different direction. It was made to switch directions intemitenly. Just another thing people come up with from time to time, to give the impression that their brain is working better than the rest of us. Try something better to fool me.

There is NO optical illusion here.The animation spins one way for a period of time and then the other,and then at different time intervals.

You can do this with your own hands.Pretend that you are opening a large bottle cap.Rotate many times one way to open the cap then without pausing rotate to close the cap.Your hand goes left to right and right to left in both cases i.e they are always moving in opposite directions but it is the ‘jerk’ on either direction(when either opening or closing) which gives the illusion of clockwise movement or anticlockwise movement.